A debut British novelist has been selected over American literary heavyweight Toni Morrison for the shortlist for this year's Orange prize for fiction.

Samantha Harvey's first novel, The Wilderness, the story of a man in his early 60s struggling to hold on to his identity as Alzheimer's takes hold of his mind, was chosen by judges for the six-strong Orange shortlist, ahead of Nobel prize for literature winner Morrison's 17th century slave trade novel, A Mercy. The £30,000 women-only prize looks to reward excellence, accessibility and originality in writing.

Harvey, who completed an MA in creative writing in 2005, is up against American author Marilynne Robinson and her follow-up to the Pulitzer prize-winning Gilead, Home, on a shortlist dominated by US authors. Home tells the story of Jack Boughton, godson and namesake of Gilead's protagonist John Ames.

Also in the running are New Yorker Ellen Feldman with her third novel Scottsboro, a fictionalisation of the infamous Scottsboro case in which nine black youths were arrested for the supposed rape of two white girls, and the American author Samantha Hunt for The Invention of Everything Else, a fictionalised account of the relationship between the brilliant Serbian inventor Nikola Tesla and a young woman who meets him at the end of his life.

"We were right down to the wire on several of the books and choosing just six was far harder than I had imagined, but we all left the judging room proud of the list we have chosen," said the chair of judges, broadcaster Fi Glover. "We have stretched our heads getting to this shortlist."

The shortlist is rounded out by two critically acclaimed writers, the Pakistani author Kamila Shamsie and the Irish writer Deirdre Madden, who was previously shortlisted for the Orange for her novel One by One in the Darkness in 1997.

Madden makes the running with her seventh novel, Molly Fox's Birthday, in which a playwright reflects on how her life has intertwined with those of two friends, the celebrated actor Molly Fox, and their mutual friend Andrew. Shamsie is shortlisted for Burnt Shadows, a decades-spanning novel which travels from the nuclear detonation in Nagasaki in 1945 to post-9/11 Afghanistan, tracing the stories of three families.

The winner of the prize, who receives a cheque for £30,000 and a bronze statue known as the Bessie, will be announced on 3 June. Last year Rose Tremain took the award with The Road Home, joining a roster of previous winners which includes Chimamanda Ngozi Adichie, Zadie Smith and Lionel Shriver.

Glover is joined on the judging panel by entrepreneur Martha Lane Fox, novelist Bidisha and journalists Kira Cochrane and Sarah Churchwell.